Ignition coil



Sept. 27, 1938. Q RENGWALD 2,131,483

IGNITION COIL Filed June 50, 1933 Patented Sept. 27, 1938 UNITED STATES PATENT OFFICE IGNITION COIL Application June 30, 1933, Serial No. 678,377

16 Claims.

This invention relates to induction coils, and more particularly to coils of this type employed for ignition purposes in automotive vehicles, stationary internal combustion engines and the like, in which situations the coils are subjected to considerable mechanical vibration and rough usage.

In coils of this type, the cost of manufacture, including the cost of materials and the cost of assembling the various elements of the coil into the coil unit, is of material importance. The reduction of the number of elements required, or of the number of operations necessary for assembling the coil, results in decreasing this cost of manufacture. However, it must be remembered that the mechanical and the electrical efficiency of the coil must not be sacrificed in order to attain economy of manufacture, since a coil of this type is subjected to rigorous operation when in actual use.

The present invention, therefore, includes among its objects the simplification of construction of an induction coil of this type, and improved efiiciency of the coil, whereby the cost of manufacture may be materially reduced.

In the preferred embodiment of the present invention, I therefore provide a coil which is quickly and economically assembled, requiring a relatively small number of assembling operations,

and which is of cheap yet substantial construction, and has increased mechanical and electrical efficiency because of certain novel features of structure which provide for effective immersion of the entire coil assembly in a suitable insulating compound, and certain features of assembly which eliminate unnecessary moulding and finishing operations.

One feature of the present invention resides in the use of a drawn metal shell into which the entire coil assembly is placed, which shell is secured to the insulating cover or cap member of the coil in a simple and positive manner, eliminating the use of rolled edges, auxiliary flanged members, anchoring means, solder, welding or the like, which has been used heretofore for effecting engagement between the shell and the cap member.

In connection with the use of this shell, I provide in the bottom thereof a base member which has only point support upon the filleted edges of the base or bottom of the shell, thereby spacing the member above the base of the shell to an extent determined by the radius of the fillet. In

this manner, heated insulating compound may be poured into the shell and will enter beneath the base member and form an effective continuous insulating seal on all surfaces of the base member which supports the coil assembly, and will also thus drive out any air tending to remain in the bottom of the shell, which is of decided advan- 5 tage in increasing the efficiency of the coil units.

In order to reduce the cost of manufacture and to expedite the assembly of the coil unit, the cap member is provided with the customary central bore for receiving the high tension leads. 10 However, in the present invention, this is counterbored to receive a cup-shaped shell member similar to a brush holder shell, which extends upwardly therein, the upper defining edge of the shell member being spaced a slight distance be- 15 low the shoulder formed by the counterbore to define an annular recess. This recess is adapted to receive a correspondingly enlarged portion of the connecting conductor tip, in order to lock the conductor in engaged position within the cap 20 member.

I also preferably provide a spacing member or anchoring baffle formed of fibrous material or the like, such as stiff paper, which is so shaped as to extend about and separate the coil leads 5 to hold them in segregated position, and is itself adapted to be held firmly in position by engagement with the lower edge of the cap member when the cap is secured to the shell.

Another advantage of the present invention 30 resides in providing a construction whereby the secondary or high tension lead may be insulated from the laminated central core, or may be grounded to the internal magnetic circuit of the coil, without altering the construction of the 5 coil, or its assembly, merely by changing the position of the coil laminations forming the internal magnetic circuit. The coil laminations are adapted to be anchored in insulating compound to prevent them from vibrating due to 40 exciting current.

Other objects and advantages of the present invention will appear more fully from the following detailed description, which, taken in connection with the accompanying drawing Will dis- 45 close to those skilled in the art the construction and operation of a preferred embodiment of my invention.

In the drawing:

Figure 1 is a top plan view of the cap or cover 50 member for the coil or shell;

Figure 2 is a sectional elevational view of the coil of the present invention;

Figure 3 is a sectional view of the coil assembly taken substantially on line 3-3 of Figure 2; 5

Figure 4 is a fragmentary sectional View of a modified form of the invention;

Figure 5 is a sectional view taken substantially on line 5-5 of Figure 2; and

Figure 6 is a view showing the method of grounding the high tension lead to the laminated core forming the internal magnetic circuit of the coil.

Referring now in detail to the drawing I preferably form the coil by winding upon an insulating tube indicated at It a plurality of layers of fine wire which provide the secondary winding H. These layers of wire are insulated from each other by thin strips of non-conductive material such as paper, fiber, or other material indicated at 12, the margins of the insulating strip extending beyond the secondary winding as shown in Figure 2.

It will be noted that the insulating tube i8 extends for a considerable distance above the upper end of the secondary winding l and paper strip 12, and also extends slightly therebelow.

A second insulating tube I5 is disposed about the secondary winding ll, extending upwardly to a point adjacent the upper end of the paper strip 52, and extending downwardly beyond the winding. Upon this tube l5 are wound a plurality of layers of relatively heavy wire to provide the primary winding l6, which, as shown in Figure 2, substantially encircles the tube IE3 at its middle portion. The layers of wire forming the primary winding are separated by suitable insulating strips of thin paper or fibrous material, as shown at H, in the same manner as described in connection with the secondary winding. An insulating shield between the core and the external magnetic circuit is provided by the spacing of the secondary winding with respect to the magnetic material and the insulation of the primary winding.

To provide the external magnetic circuit, a plurality of substantially semi-circular cylindrical sections 28 are provided, which are formed of thin sheets of metal, and which are overlapped to form a substantially continuous magnetic field about the primary winding I6, as shown in detail in Figure 3, which discloses the manner in which the strips forming the magnetic circuit 20 are overlapped to form a surrounding yoke. These strips extend from the bottom end of tube slightly above the upper end thereof, and the gaps between respective strips are disposed out of radial alignment whereby no through gap is formed at any point in the circumferential extent of the field, the sheets overlapping in such manner as to form a closed field about the secondary winding.

I preferably bind the strips in position by merely rolling the coil member and yoke within a strip of gummed paper tape or the like, indicated at 2|, which is moistened and which securely holds the assembled secondary, primary and magnetic circuits in definite relative position.

Within the insulating tube I0 I preferably provide a plurality of laminated iron strips indicated at 23, forming the core for the internal magnetic circuit. The individual laminations forming the core 23 are movable with respect to each other, and have sliding engagement with the surface of the next adjacent laminations, whereby they may be moved from the position shown in Figure 3 to the position shown in Figure 6, in order to provide either a grounded or ungrounded high tension lead. This arrangement also allows the insulating compound to enter the tube [0 to anchor the core laminations in position.

The coil assembly, comprising the core 23, the primary and secondary windings, and the external magnetic circuit 20, is then disposed within the shell member 25, which shell member is preferably an ordinary drawn metal shell having a smooth exterior surface. As will be noted, the base of the shell 25, indicated at 26, is integrally connected to the cylindrical portion of the shell 25 by a smooth curved portion forming a filleted surface indicated at 27. In this manner, I am enabled to dispose the insulating base members 28, which are preferably formed of fibre or other suitable insulating material, and which are of rectangular or other polygonal shape, in position within the shell member 25 with the corners of the members 28, indicated at 29, being disposed at the edges 27 on the base 26 in such manner that the members 28 are spaced above the inner surface of the base 26, providing a space indicated at 30 therebetween. Also, because of the square or polygonal shape of the members 28, spaces 3| are provided between the cylindrical walls of the shell 25 and the periphery of the members 28. It is to be understood that only a single base member 28 may be provided, if desired. The coil assembly is adapted to be placed in position on the member 28, as shown in Figure 2, and is supported thereby.

In assembling the unit, a small amount of insulating compound or wax is poured into the shell, which has the polygonally shaped insulators 28 therein, the wax surrounding these members. The winding is then inserted and the wax is forced up within the tube 10 to anchor the core in position. This is advantageous in that it prevents vibration of the core, which eventually tends to loosen and injure the coil winding. The wax is also poured on top of the winding unit after it is assembled in the case. Also, a portion of the compound enters between the paper strips l2 at the lower end of the secondary winding II, and between the paper strips I! at the lower end of the primary winding I6, serving to secure the strips in fixed position, and also serving to provide a sealing engagement about the insulating base 28 and about the tube and within the tube l8. Further, by means of the spacing of the base members 28 from the lower surface of the shell, any air bubbles or the like which would ordinarily be trapped therein are driven outwardly, and escape upwardly within the tube It! to the upper end of the shell 25, this method providing a continuous and substantially solid insulating seal at all portions of the coil assembly, with no air bubbles trapped therein.

Considering now in detail the leads for the various windings of the coil, the entering lead for the primary winding is indicated by the numeral 35, while the end of the primary winding is indicated by the lead 36 extending upwardly from the opposite side thereof. The wire leading to the beginning of the secondary winding is indicated at 31, being disposed within the insulation 38, which comprises varnished tubing or the like, and the end of the secondary winding is indicated by the lead 39 which is taken off from the winding adjacent the point that the entering lead to the primary winding enters the winding.

In order to separate these various leads, and to anchor them in fixed position, I preferably provide what I term a yoke anchor or high tension insulating bafile, comprising the paper or fibrous strip 40, as shown in detail in Figures 2 and 3, which is curved about the insulating tube 10, and has its ends turned back, as indicated at 4| and 42, to enclose respectively, the leads and 39 at one side of the tube 10, and the lead 36 at the opposite side of the tube 10, the middle portion 43 of the anchor serving to hold the anchor in position about the insulating tube 10. This yoke also serves to hold the assembly in position, being held in place by the top when the unit is assembled.

The coil is secured in position upon a vertical surface by means of the bracket 44 extending about the shell 25 and having the flattened ends 54 provided with suitable apertures to receive securing means for fixing the bracket in position.

A suitable cap member, indicated at 45, which is formed of porcelain, Bakelite, or other similar insulating material, is provided with a lower depending flange 46, and with an outer annularly extending ring portion 41. Between the ring portion 41 and the lower depending flange 46 an annular groove 48 is provided, which is adapted to receive the upper end of the shell 25, this end being pressed or crimped into the groove 48 by any suitable tool for clamping the shell to the coil top. I'his may be accomplished in any desired manner.

Diametrically opposed portions of the cap are provided with rounded boss portions substantially coplanar with the lower flange 46, which are adapted to form recesses indicated at 49 for receiving the terminal members 50. The members 50 extend upwardly through a pair of washers 5!, and are held in position by means of the nuts 52 threaded thereon, as shown in Figure 1, when a porcelain top is used. With moulded Bakelite, however, inserts only would be necessary. The upper portion of the cap member 45 is recessed, and has the extending shoulder portions 53 adapted to form protecting openings which receive the terminal members 50. The terminal members 59 are preferably held in position by means of sealing wax or the like, in order to prevent rotation thereof. It will thus be noted that the terminals are recessed, instead of projecting outwardly from a bossed surface, as is common in the prior art. The leads 35 and 39 are adapted to be led up through one of the members 50 and soldered thereto, while lead 36 is led up through the other member.

Extending centrally of the cap member 45 is the bore indicated at 55, which is adapted to receive the high tension conductor indicated at 56, which is encased within a suitable sheath 51. The bore 55 is counterbored, as shown at 58, to receive a cup-shaped drawn shell member 59, corresponding generally to a brush shell, which is of such a vertical extent as to have its upper defining edge spaced slightly below the shoulder formed between the counterbore 58 and the bore 55, this spacing providing an annular groove indicated at 60 for receiving the enlarged portion 61 of a resilient split cup-shaped member forming the high tension lead tip, in order to secure the same in position. This is shown more clearly in Figure 4.

The lead 31 is brought upwardly, and is anchored into the lower flanged portion or base of the shell 59, as indicated at 62. The contacting tip of the high tension lead 56 is adapted to be snapped into engagement within the bore 55 in such manner that the end thereof comes into contact with the tip 62 of the lead 31 to provide for high tension connection thereto. This provides for snap engagement of the conductor end within the shell 59, and thus eliminates the provision of any special locking means, clamping devices, or other similar means for securing positive engagement of the conductor tip within the bore.

Preferably, in order to provide a perfectly sealed coil assembly, after the insulating compound has been poured into the shell 25 to seal the coil assembly therein, and the cover has been assembled in position, the entire assembly is inverted for an instant, and then allowed to remain upright, thus placing a thin film of the insulating compound, indicated at 65, over the inner extending portions of the cap member 45, in order to seal the same, and to thus provide a substantially air-tight sealed coil assembly. The upper end of the shell 25 is then crimped into groove 48. The flange 46 is preferably provided with a small notched portion indicated at 64, which is adapted to be placed over shells of the type having a lap joint, although I prefer to use a drawn type of shell.

The core member 23 may be placed into grounded position with respect to the lead 31, or in ungrounded position with respect thereto, by merely slapping the coil assembly in the hand, since the shock is sufficient to allow the individual laminations of the core to slide into the corresponding positions shown in Figures 6 and 3, before the shell is filled with the insulating compound. By eliminating the insulating tubing 38, the core is directly and electrically connected to the conductor 31, and a contact between the core and the high tension terminal 59 can thus be effected Without requiring an extension of conductor 31, or an auxiliary connecting means. If an insulated core is desired, the tubing 38 is provided, and the core laminae are disposed in the position shown in Figure 3. In both instances, after the core laminae have been positioned, the tube I8 is filled with insulating wax to anchor them in position, since at slow speed operation of the induction coil the current impulses tend to shift the laminae, and they are likely to twist around and break off the high tension lead, or destroy its insulating tubing, unless held in place by this wax.

If it is desired to provide a coil assembly which is so constructed as to eliminate interference with radio operation in a vehicle or the like, the construction is slightly altered as shown in detail in Figure 4. In this instance, the only change in construction is made in connection with the lead 31. This lead is provided, adjacent its upper end, with a high resistor indicated at 10, which resistance is provided with soldered terminal ends, one of the ends being soldered to the lead 31, and the other end being soldered to an auxiliary lead 31 leading to the drawn shell member 59 and forming the contact portion.

The resistor 19, having the soldered ends, can thus be quickly fixed into position, and preferably is provided with a wax seal in order to eliminate corona effects. An insulating tube of any suitable material, indicated at 1|, is adapted to extend between the lower portion of the shell 59 and the upper portion of the core 23, this shell serving to insulate the resistor 10 from the remaining portions of the coil assembly, but being of sufficient size to allow wax to flow freely around the resistor for sealing it against corona effects. The coil in this instance is also filled with insulating compound to form sealing means and to drive out any air that may be present therein.

Inasmuch as the discharge from a high tension terminal is of a high frequency oscillatory nature, which is extremely undesirable adjacent radio receiving circuits, the resistance '10 is employed to damp the oscillatory nature of the discharge and prevent crackling or static effects being picked up by the radio circuit. Thus, instead of a high frequency oscillating spark discharge from the coil, a. substantially single non-oscillatory power discharge is provided by means of this resistance.

It is apparent that I have provided an induction coil of the type described which is provided with simplified means for securing the shell carrying the coil assembly to the cap or coil through which the leads are adapted to extend. Also, in con nection with the use of this type of shell member, I have provided a new manner of supporting the base member therein whereby all air bubbles and the like will be driven from the bottom, of the shell, and a continuous and efiective seal will be formed by the insulating compound which is poured into the shell, because of the openings by which it may pass downwardly intothe very bottom of the shell.

Also, by the use of the metal cap member 59, the engagement of the high tension lead within the coil top is effected without the provision of auxiliary means ordinarily provided for effecting this engagement. Other advantageous features of construction make it possible to produce the induction coil of the present invention at a much lower cost of manufacture than is possible with other types of induction coils of similar characteristics of which I am aware.

Inasmuch as it is apparent that there may be changes or modifications made in the construction of the preferred embodiment of my invention, as disclosed, without in any manner changing the scope or spirit of the invention provided thereby, I do not intend to limit my claims to the exact structural features which I have disclosed, but only in so far as they define the invention in the appended claims.

I claim:

1. A coil top for an. induction coil having a central passage provided with a counterbore, and a drawn metal cup-shaped shell of an internal diameter substantially equal tothe diameter of said passage inserted into said counterbore and having its upper open edge spaced slightly beneath the shoulder formed between said counterbore and said passage to provide an annular groove in said passage between the upper peripheral edge of said shell and said shoulder.

2. In a coil of the class described, a drawn metal shell of cylindrical form having an integral base joined to the cylindrical portion thereof, and a planar insulating member disposed within said shell and spaced from the base thereof by point contact upon the filleted edge of said base.

3. In a coil of the class described, a. drawn metal shell of cylindrical form having an integral base joined to the cylindrical portion, thereof, and a planar insulating member disposed within said shell and spaced from the base thereof by point contact upon the filleted edge of said base, said insulating member being formed to provide communication from said shell into the space between said member and the base of the shell along the inner periphery thereof.

4. In a coil, an intermediate article of manufacture comprising a secondary winding supported upon an insulated tube, a core providing the internal magnetic circuit for said coil disposed within said tube and comprising a plurality of corresponding metallic strips disposed loosely in said tube and shiftable to opposite sides of said tube, and a high tension lead from said winding entering said tube and extending upwardly therethrough along the edges of the strips at one side of the core, said lead being adapted to be engaged by moving said strips in one direction toward said one side of the tube and to be electrically separated from said lead by shifting said strips toward the other side of said tube.

5. In combination, a coil top for an induction coil having a high tension lead, a central passageway in said top for receiving a high tension conductor, a counterbore in the lower end of said passageway, and a drawn metal cup-shaped shell of uniform diameter adapted to be inserted in said counterbore, said high tension lead entering into the base of said shell, the upper defining edge of said shell being spaced slightly beneath the shoulder formed between the counterbore and the passageway to define an annular groove between said edge and said shoulder for receiving an enlarged annular shoulder formed on said high tension conductor within said passageway to lock said conductor in said passageway.

6. An induction coil of the class described comprising an enclosing metallic cylinder, a primary winding within said cylinder and disposed beneath the upper edge thereof, a secondary winding disposed within said primary winding and supported on an insulating tube, said tube extending upwardly above said windings, leads from said windings extending upwardly therefrom, and an insulating flexible bafiie member disposed in contact with said tube and having end portions segregating said leads.

'7. An insulating baflle member for a coil having primary and secondary leads extending upwardly into an annular recess provided between an inner insulating tube and an outer metallic cylinder, comprising a fiber member having a central portion extending tangential to a portion of the periphery of said inner tube and having its ends reversely bent into tangential contact with the inner portion of said cylinder, said member segregating said leads in insulated position with respect to said cylinder.

8. In combination, in an induction coil, a drawn metal shell, a polygonal insulating member having point support within and spaced from the bottom of said shell, a coil assembly supported upon said member and having an internal magnetic core formed of laminated metallic strips shiftable with respect to each other to provide a grounded or ungrounded coil, a coil top, and means in said top for receiving the crimped upper edge of said shell to secure said top to said shell.

9. In an ignition coil having a core, a secondary winding and a lead from said winding leading to a drawn metal shell disposed in the central passageway of a coil top secured to said coil, means for preventing radio interference by said coil comprising a high resistance member interposed between the ends of said lead, and an insulating tube enclosing said resistance member and said lead, said insulating tube engaging said core at one end and said drawn metal shell at the other end.

10. In an ignition coil assembly, a shell a coil assembly disposed within said shell and having extending leads, a coil top for said shell, and independently adjustable insulating means for segregating said leads and for holding said coil assembly in fixed position comprising a flexible baffle member spaced between the top of said assembly and said coil top.

11. In a coil of the class described, a drawn metal cylindrical shell having an integral planar base joined to the cylindrical portion thereof by a smooth fillet, and a polygonally shaped planar insulating member having point contact with the cylindrical wall of said shell and spaced away from said base by said fillet to provide for enentrance of insulating compound into contact with said base about the edges of said member.

12. The combination with an induction coil confined within a cylindrical casing having a planar base joined thereto by an annular fillet, of means for spacing said coil from the base of said casing comprising a square planar insulating member disposed above the plane of said base and supported by point contact with the inner periphery of said fillet, said member providing for passage of insulating compound into the space between said base and said member around the defining edges of said member.

13. An insulating baiile member for a coil having leads extending outwardly into an annular recess, comprising a flexible member disposed in said recess and having an arcuately curved central portion, and integrally formed end portions doubled back to form a plurality of spaced segregated lead receiving means.

14. In an ignition coil, a cup-shaped shell, a coil assembly therein comprising a substantially cylindrical secondary winding, a central insulating passing through said winding, a cylindrical tube enclosing said winding and extending outwardly at one end thereof, a primary winding' about said tube including sheets of insulation wound therewith and extending the length of said tube whereby the insulation of the primary winding overlaps the end of the secondary winding and forms a cylindrical chamber thereabout, a casing for receiving said assembly, and

spacing means at one end of said casing supporting said extending end of said tube above the closed end of said shell and closing said chamber, whereby said chamber has communication with the top of said shell only through said central passage.

15. In an ignition coil, a coil assembly comprising a substantially cylindrical secondary winding, a central insulating passage through said winding, a cylindrical tube enclosing said winding and extending outwardly at one end thereof, a primary winding about said tube including sheets of insulation wound therewith and extending the length of said tube whereby the insulation of the primary winding overlaps the end of the secondary winding and forms a cylindrical chamber thereabout, a casing for receiving said assembly, said tube cooperating with one end of said casing to close said cylindrical chamber so that the latter has communication with the other end of said casing only through said central passage.

16. In an ignition coil, a coil assembly therein comprising a substantially cylindrical secondary winding, a central insulating passage through said winding, a cylindrical tube enclosing said winding and extending outwardly at one end thereof, a primary winding about said tube including sheets of insulation wound therewith and extending the length of said tube whereby the insulation of the primary winding overlaps the end of the secondary winding and forms a cylindrical chamber thereabout, a casing for receiving said assembly, said tube cooperating with one end of said casing to close said cylindrical chamber so that the latter has communication with the other end of said casing only through said central passage, a coil top disposed over the open end of said casing, and spacing means disposed between said coil top and the ends of said windings opposite the extending portions of said tube.

CLARENCE RINGWALD. 

